Handle implicit convert expression in LINQ update with anonymous type.

Author: gliljas

src/NHibernate.Test.VisualBasic/Issues/GH3716/Entity.vb

@@ -0,0 +1,7 @@
+Namespace Issues.GH3716
+    Public Class Entity
+        Public Overridable Property Id As Guid
+
+        Public Overridable Property Date1 As Date?
+    End Class
+End Namespace

src/NHibernate.Test.VisualBasic/Issues/GH3716/Fixture.vb

@@ -0,0 +1,58 @@
+Imports NHibernate.Linq
+Imports NUnit.Framework
+
+Namespace Issues.GH3716
+    <TestFixture>
+    Public Class Fixture
+        Inherits IssueTestCase
+
+        Protected Overrides Sub OnSetUp()
+
+            Using session As ISession = OpenSession()
+
+                Using transaction As ITransaction = session.BeginTransaction()
+
+                    Dim e1 = New Entity
+                    e1.Date1 = New Date(2017, 12, 3)
+                    session.Save(e1)
+
+                    Dim e2 = New Entity
+                    e2.Date1 = New Date(2017, 12, 1)
+                    session.Save(e2)
+
+                    Dim e3 = New Entity
+                    session.Save(e3)
+
+                    session.Flush()
+                    transaction.Commit()
+
+                End Using
+
+            End Using
+        End Sub
+
+        Protected Overrides Sub OnTearDown()
+
+            Using session As ISession = OpenSession()
+
+                Using transaction As ITransaction = session.BeginTransaction()
+
+                    session.Delete("from System.Object")
+
+                    session.Flush()
+                    transaction.Commit()
+
+                End Using
+
+            End Using
+        End Sub
+
+        <Test>
+        Public Sub ShouldBeAbleToUpdateWithAnonymousType()
+
+            Using session As ISession = OpenSession()
+                session.Query(Of Entity).Update(Function(x) New With {.Date1 = Date.Today})
+            End Using
+        End Sub
+    End Class
+End Namespace

src/NHibernate.Test.VisualBasic/Issues/GH3716/Issues.GH3716.Mappings.hbm.xml

@@ -0,0 +1,11 @@
+<?xml version="1.0" encoding="utf-8" ?>
+<hibernate-mapping xmlns="urn:nhibernate-mapping-2.2" assembly="NHibernate.Test.VisualBasic" namespace="NHibernate.Test.VisualBasic.Issues.GH3716">
+
+	<class name="Entity">
+		<id name="Id">
+			<generator class="guid.comb"/>
+		</id>
+		<property name="Date1" />
+	</class>
+
+</hibernate-mapping>

src/NHibernate/Linq/DmlExpressionRewriter.cs

@@ -25,10 +25,10 @@ void AddSettersFromBindings(IEnumerable<MemberBinding> bindings, string path)
 				switch (node.BindingType)
 				{
 					case MemberBindingType.Assignment:
-						AddSettersFromAssignment((MemberAssignment)node, subPath);
+						AddSettersFromAssignment((MemberAssignment) node, subPath);
 						break;
 					case MemberBindingType.MemberBinding:
-						AddSettersFromBindings(((MemberMemberBinding)node).Bindings, subPath);
+						AddSettersFromBindings(((MemberMemberBinding) node).Bindings, subPath);
 						break;
 					default:
 						throw new InvalidOperationException($"{node.BindingType} is not supported");
@@ -53,10 +53,10 @@ void AddSettersFromAnonymousConstructor(NewExpression newExpression, string path
 				switch (argument.NodeType)
 				{
 					case ExpressionType.New:
-						AddSettersFromAnonymousConstructor((NewExpression)argument, subPath);
+						AddSettersFromAnonymousConstructor((NewExpression) argument, subPath);
 						break;
 					case ExpressionType.MemberInit:
-						AddSettersFromBindings(((MemberInitExpression)argument).Bindings, subPath);
+						AddSettersFromBindings(((MemberInitExpression) argument).Bindings, subPath);
 						break;
 					default:
 						_assignments.Add(subPath.Substring(1), Expression.Lambda(argument, _parameters));
@@ -121,9 +121,11 @@ public static Expression PrepareExpressionFromAnonymous<TSource>(Expression sour
 			if (expression == null)
 				throw new ArgumentNullException(nameof(expression));
 
-			// Anonymous initializations are not implemented as member initialization but as plain constructor call.
+			// Anonymous initializations are not implemented as member initialization but as plain constructor call, potentially wrapped in a Convert expression
 			var newExpression = expression.Body as NewExpression ??
-				throw new ArgumentException("The expression must be an anonymous initialization, e.g. x => new { Name = x.Name, Age = x.Age + 5 }");
+				(expression.Body is UnaryExpression unaryExpression && unaryExpression.NodeType == ExpressionType.Convert && unaryExpression.Operand is NewExpression newExpressionOperand
+					? newExpressionOperand
+					: throw new ArgumentException("The expression must be an anonymous initialization, e.g. x => new { Name = x.Name, Age = x.Age + 5 }"));
 
 			var instance = new DmlExpressionRewriter(expression.Parameters);
 			instance.AddSettersFromAnonymousConstructor(newExpression, "");